The pathologies treated by VKA are more common in the elderly. They are also more vulnerable to falls, overdoses of these treatments because their pharmacokinetics is amended by polypharmacy, malnutrition, less protein binding. The relative risk of bleeding is multiplicated by two beyond 70 years. Despite the emergence of new anticoagulants in the prevention of complications of arrhythmia (this disorder affect nearly 10% of the population aged over 80 years), VKA remains prevalent because these new drugs have renal elimination that can not be monitored, and can not be dialysable, have no antidote and represent a daily cost about 30 times the VKA.